Wafer die separation

ABSTRACT

A method of singulating a wafer starts with fracturing the wafer. The method may also include attaching the dicing tape sheet to a ring frame; relatively raising a portion of the dicing tape sheet supporting the wafer with respect to the ring frame; and attaching support tape to the ring frame and the dicing tape sheet.

CROSS REFERENCE TO RELATED APPLICATION

This application is a Continuation of and claims priority to U.S. patentapplication Ser. No. 13/894,177 filed on May 14, 2013. Said applicationherein incorporated by reference in its entirety.

BACKGROUND

Integrated circuit “dies” or “dice” are small cubes of semiconductormaterial such as silicon that have various interconnected electricalcircuits formed therein. Each die typically has a metalized surfacelayer with electrical contact regions thereon that allows the die to beconnected to other electronic components. Integrated circuit dice areproduced by “singulating” (“dicing”) a unitary semiconductor waferhaving identical circuits formed in adjacent regions thereof that arearranged in a rectangular generally waffle-shaped grid. Saw cuts orlaser fractures are made along “saw streets” to cut the wafer into dice.A diced wafer is often supported on a deformable sheet known as dicingtape. The dicing tape may be stretched by force applied to its outerperimeter. Stretching the dicing tape causes the diced wafer supportedon it to expand laterally, thereby separating the dice. The separateddice may then be picked up, one at a time, by pick and place machines orthe like. With very small dice, i.e., less than about 1.0 mm, currentmethods of expanding the dicing tape tend to provide insufficient spacebetween dice, or the space provided shrinks sufficiently after initialexpansion, such that handling of the dice is difficult and often endswith damage to adjacent dice.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic top isometric view of a wafer, illustratingsingulation thereof with a stealth laser.

FIG. 2 is a schematic bottom isometric view of a wafer, illustratingmounting of a dicing tape sheet and ring frame.

FIG. 3 is a schematic top isometric view of a wafer, dicing tape sheetand ring frame.

FIG. 4 is a schematic cross sectional elevation view of a wafer supporttable, dicing tape sheet, wafer and ring frame with the wafer in anunseparated state.

FIG. 5 is a schematic cross sectional elevation view of a wafer supporttable, dicing tape sheet, wafer and ring frame with the wafer supporttable raised relative to the ring frame and with the dicing tape sheetstretched and with the wafer in an expanded state.

FIG. 6 is a schematic cross sectional elevation view of the wafersupport table, dicing tape sheet, wafer and ring frame in the stateillustrated in FIG. 5 and further showing a support tape ring just priorto application thereof.

FIG. 7 is a schematic cross sectional elevation view of the wafersupport table, dicing tape sheet, wafer and ring frame of FIG. 6, withthe support tape ring applied to the ring frame and dicing tape sheetand with the wafer support table lowered relative to the ring frame.

FIG. 8 is a top plan view of the dicing tape sheet, wafer, ring frameand support tape in the state illustrated in FIG. 7.

FIG. 9 is a detail view of the assembly of FIG. 7.

FIG. 10 is a top plan view of an another embodiment of dicing tapesheet, wafer, ring frame and support tape in which circumferentiallyextending strips of support tape are used.

FIG. 11 is a top plan view of still another embodiment of dicing tapesheet, wafer, ring frame and support tape in which radially extendingstrips of support tape are used.

FIG. 12 is a top plan view of still another embodiment of dicing tapesheet, wafer, ring frame and support tape in which chord wise extendingstrips of support tape are used.

FIG. 13 is a flow chart of a method of separating dice of a singulatedwafer that is supported on a dicing tape sheet.

FIG. 14 is a flow chart of a method of separating dice of a singulatedwafer that is supported on a relatively elastically deformable dicingtape sheet.

DETAILED DESCRIPTION

In general, this specification discloses, as illustrated by FIGS. 4-8and 13, a method of separating dice 32, 34 of a singulated wafer 30 thatis supported on a dicing tape sheet 10. The method includes attachingthe dicing tape sheet 10 to a ring frame 40, as shown at block 201 ofFIG. 13. The method also includes, as shown at block 202 of FIG. 13,relatively raising a portion 13 of the dicing tape sheet 10 supportingthe wafer with respect to the ring frame 40. The method further includesattaching support tape 60 to the ring frame 40 and the dicing tape sheet10, as shown at block 203 of FIG. 13.

FIG. 1 is a schematic top isometric view of a wafer 30, illustratingsingulation thereof with a stealth laser 20. The stealth laser 20,produces fractures in the wafer that form a plurality of singulationlines 21, 22, 23, 24, etc. that form a rectangular grid and divide thewafer 30 into a plurality of dies or dice 32, 34, etc. The wafer 30 mayinstead be singulated by saw cutting. Both stealth laser and saw cuttingsingulation are now in the art and are thus not further discussedherein.

FIG. 2 is a schematic bottom isometric view of a wafer, illustratingmounting of a generally circular dicing tape sheet 10 on a back surface36 of the wafer 30. The dicing tape sheet 10 has a tacky top surface 11that is attached to the back surface 36 of the wafer 30. The dicing tapesheet 10 has a non-tacky bottom surface 12. A ring frame 40 is attachedat a bottom surface 41 thereof to the tacky top surface 11 of the dicingtape sheet 10 at its periphery. Thus an assembly is formed asillustrated in FIG. 3 in which a generally circular wafer 30 issupported on a generally circular dicing tape sheet 10. Both the wafer30 and most of the circular dicing tape sheet 10 are circumscribed bythe ring frame 40. Such an assembly is known in the art.

As illustrated by FIG. 4, the assembly of FIG. 3 may be positioned on agenerally flat top surface 51 of a support table 50, such that the tabletop surface 51 is below a portion 13 of the dicing tape sheet 10 thatsupports the wafer 30 and associated dice 32, 34. An outer annularportion 15 of the dicing tape sheet 10 that extends out in coplanarrelationship with portion 13 and the ring frame 40 are not supported bythe table top surface 51. An alternate support such as a supportring/stand (not shown) or a human hand (not shown) may support the ringframe 40 and dicing tape sheet portion 15.

Next, as illustrated by FIG. 5, the table 50 is raised relative to thering frame 40. As a result the entire dicing tape sheet 10 is stretchedradially and, as a result, the dice 32, 34 mounted on inner dicing tapesheet portion 13 are radially spread apart. In other words, thesingulation lines 21, 22, 23, 24, etc. become wider. In one embodimentthe width of each singulation lines 21, 22, 23, 24, etc. is about 0.020mm or more after the expansion shown in FIG. 5.

As shown by FIG. 6, a ring of support tape 60 is then positioned overthe ring frame 40 and an annular part of the outer annular portion 15 ofthe dicing tape sheet 10. The support tape has a smooth, non-tackysurface 61 and a tacky surface 63. The tacky surface 63 of the supporttape 60 is then pressed onto the ring frame 40 and the dicing tape sheet10 when they are positioned as shown in FIG. 6. The table 50 is thenraised relative to the ring frame 40 so that the dicing tape sheet 10 isreturned to a generally planar configuration as shown in FIGS. 7 and 8.Dimensional parameters of the ring frame 40, support tape 60, dicingtape sheet 10 and the wafer are illustrated in FIG. 9. In onenonlimiting embodiment these parameters may have the following values:a=15.0 mm, b=5.0 mm, c=10.0 mm, d=1.6 mm, e=5.0 mm, f=10.0 mm, g=23.0mm, h=10.0 mm, i=13.0 mm, j=0.050 mm to 0.900 mm, and k=0.180 mm. Thethickness of the dicing tape may be 0.09 mm. It will be understood thatthese dimensions are only provided to give the reader a relative senseof scale for one typical embodiment.

These dimensions will of course vary with wafers of different diametersand thicknesses and with different types of singulation and withdifferent sizes and materials used for the dicing tape sheet and thesupport tape. In some embodiments the dicing tape sheet is made fromrelatively stretchable (elastic) material, such as polyvinyl chloride(PVC) or polyolefin (PO) and the support tape is made from relativelynonstretchable (inelastic) material such as polyethylene terephthalate(PET).

FIG. 10 is a top plan view of an another embodiment of dicing tape sheet10, wafer 30, ring frame 40 and support tape 60A in which a plurality ofcircumferentially (arcuately) extending support tape strips 60A₁, 60A₂,60A₃, etc. are attached to the dicing tape sheet 10 and the ring frame40 to prevent inward retraction of the dicing tape 10 and an associatedreduction in width of the spaces 21, 22, 23, 24, etc., between dice 32,34, etc.

FIG. 11 is a top plan view of an another embodiment of dicing tape sheet10, wafer 30, ring frame 40 and support tape 60B in which a plurality ofradially extending support tape strips 60B₁, 60B₂, 60B₃, etc., areattached to the dicing tape sheet 10 and the ring frame 40 to preventinward retraction of the dicing tape 10 with an associated reduction inwidth of the spaces 21, 22, 23, 24, etc., between dice 32, 34, etc.

FIG. 12 is a top plan view of an another embodiment of dicing tape sheet10, wafer 30, ring frame 40 and support tape 60C in which a plurality ofchord wise extending support tape strips 60C₁, 60C₂, 60C₃, etc., areattached to the dicing tape sheet 10 and the ring frame 40 to preventinward retraction of the dicing tape 10 with an associated reduction inwidth of the spaces 21, 22, 23, 24, etc., between dice 32, 34, etc.

In each of the above discussed embodiments the support tape 60 willreduce the amount of radial inward creep or inward retraction that thedicing tape sheet 10 would undergo without the support tape 60. As aresult, individual dies 32, 34, etc. may be picked up with aconventional pick and place machine (not shown) without damagingadjacent dice.

FIG. 14 discloses a method of separating dice of a singulated wafer thatis supported on a relatively elastically deformable dicing tape sheet.The method includes, as shown at block 221, stretching the dicing tapesheet. The method further includes, as shown at block 222, resisting atendency of the dicing tape sheet to retract from said stretching byapplying relatively nonelastically deformable support tape to the dicingtape.

Certain methods of separating dice of a singulated wafer and associatedapparatus are expressly disclosed in detail herein. Various alternativeembodiments of such methods and apparatus will occur to those skilled inthe art after reading this disclosure. The appended claims are intendedto be broadly construed so as to cover such alternative embodiments,except as limited by the prior art.

What is claimed is: 1-20. (canceled)
 21. A method of singulating a waferand separating die that are supported on a dicing tape sheet comprising:fracturing wafer to form a plurality of singulation lines dividing thewafer into a plurality of dies; attaching the dicing tape sheet to aring frame; relatively raising a portion of the sheet supporting thewafer with respect to the ring frame; and attaching a plurality ofradially extending strips of support tape to the ring frame and thedicing tape sheet.
 22. The method of claim 21, further comprisingsupporting the wafer supporting portion of the dicing tape sheet on asupport table.
 23. The method of claim 22 wherein said relativelyraising a portion of the sheet supporting the wafer with respect to thering frame comprises relatively raising the support table relative tothe ring frame.
 24. A method of singulating a wafer and separating diethat are supported on a dicing tape sheet comprising: fracturing waferto form a plurality of singulation lines dividing the wafer into aplurality of dies; attaching the dicing tape sheet to a ring frame;relatively raising a portion of the sheet supporting the wafer withrespect to the ring frame; and attaching support tape to the ring frameand the dicing tape sheet comprises attaching a plurality of chord wiseextending strips of support tape to the ring frame and the dicing tapesheet.
 25. The method of claim 24, further comprising supporting thewafer supporting portion of the dicing tape sheet on a support table.26. The method of claim 25 wherein said relatively raising a portion ofthe sheet supporting the wafer with respect to the ring frame comprisesrelatively raising the support table relative to the ring frame.
 27. Amethod of singulating a wafer and separating die that are supported on adicing tape sheet comprising: fracturing wafer to form a plurality ofsingulation lines dividing the wafer into a plurality of dies; attachingthe dicing tape sheet to a ring frame; relatively raising a portion ofthe sheet supporting the wafer with respect to the ring frame; andattaching a plurality of circumferentially extending strips of supporttape to the ring frame and the dicing tape sheet.
 28. The method ofclaim 27, further comprising supporting the wafer supporting portion ofthe dicing tape sheet on a support table.
 29. The method of claim 28wherein said relatively raising a portion of the sheet supporting thewafer with respect to the ring frame comprises relatively raising thesupport table relative to the ring frame.